http://ccmixter.org (fantastic CC remix site)
http://jamendo.com (francophone bit torrent site, 1300 CC albums, all
languages)
http://cc365.org (one Creative Commons licensed tune a day, 5 of us
blog in round robin)
There are more, but perhaps I'll save some for a later post.
Typically, with attribution, for non-commercial uses CC is good to go.
If you are making money, selling ads and the like, you might want to
contact the artists.
Something I wanted to share, but couldn't find the right moment at
Podcamp.